In the related art, electric vehicles such as electric cars or hybrid cars that travel by using motive power from a rotary electrical machine are widely known. The electric vehicles are normally provided with a battery that supplies power to the rotary electrical machine. The battery may be charged by external power supplied from an external power source. In order to perform external charging, the electric vehicle is brought into a plug-in state in which a charging plug provided on the electric vehicle is connected to the external power source.
It is known that the battery's performance is lowered when the temperature is excessively low. Therefore, in the related art, if the temperature of a battery is low at the time of the external charging, a battery temperature raising process is performed in parallel to a battery charging process (For example, see JP 2015-159633 A).
The maximum output power of the external power source differs depending on the type of facility, country, region, and the like where the external power source is installed. For example, the maximum output power supplied from the external power source is prescribed by a law of each country or by private standards (for example, JEAC, etc.), and there are some countries in which the maximum output power of the external power source is low. In addition, there are many countries and regions in which power quality is low, and thus there is often a case where a nominal power fails to be supplied.
If the charging and temperature raising processes are performed in the same manner as in a case where output power from the external power source is high when the output power from the external power source is low as described above, the charging process and the temperature raising process might fail to be adequately performed. For example, when a plug-in connection is established, the battery system normally starts charging the vehicle-mounted battery and, if necessary (if the battery temperature is low), also starts raising the battery temperature. However, when the charging and temperature raising processes are performed in parallel in a state in which the maximum output power from the external power source is low, power which can be used for charging the battery is significantly lowered, and thus a significant increase in time required for completing the charging process may result.
JP 2012-178899 A discloses a technology in which a threshold temperature is set in accordance with the maximum output power from the external power source, and if the battery temperature is not lower than the threshold temperature, only the charging process is performed without raising the temperature, and if the battery temperature is lower than the threshold temperature, only the temperature raising process is performed without charging the battery. According to this technology, the charging and temperature raising processes are not performed simultaneously.
According to JP 2012-178899 A, when the battery temperature is low, the temperature raising process is given priority over the charging process. However, when the plug-in connection is established, a user generally wants to charge the battery, but not raise the temperature. According to the technology disclosed in JP 2012-178899 A, when the battery temperature is low, the priority is given to the temperature raising process over the charging process against the intention of the user. Consequently, the battery may fail to be charged rapidly.